1. Field of the Invention
The present invention pertains, in general, to a magnetic recording medium and, more particularly, to a magnetic recording medium for recording information thereon, in which carbon is added to a FePt thin film used as an information storing unit to improve an information storing density, and a method of manufacturing the same.
2. Description of the Related Art
Generally, a material used in a magnetic recording medium for recording information thereon must have coercivity of two to five kOe and a small grain size in the consideration of magnetic recording stability and a capacity of a recording head. However, the smaller the grain size is, the poorer heat stability of the magnetic recording medium is. Thus, the magnetic recording medium must have high magnetic anisotropy so as to prevent its heat stability from being poor. In this regard, currently, a FePt thin film with an ordered structure is monitored with keen interest as a material of the magnetic recording medium for recording information thereon. The FePt thin film manufactured at room temperature has a disordered face centered cubic (fcc) structure, but the FePt thin film heat-treated at a relatively high temperature has an ordered face centered tetragonal (fct) structure with the high crystalline magnetic anisotropy.
However, the FePt thin film heat-treated at a relatively high temperature is disadvantageous in that it has a large grain size and an arrangement of grains is irregular even though it has an ordered structure. Accordingly, various studies have been made of desirably heat-treating the FePt thin film or adding additional materials to the FePt thin film to secure physical properties suitable to the material of the magnetic recording medium.
For example, U.S. Pat. No. 5,989,728 (Nov. 23, 1999, Coffey et al.) briefly mentions that the addition of specific substances such as carbon to the FePt thin film might induce a fine structure of a FePt thin film, thereby reducing a noise of a magnetic recording medium including the FePt thin film. However, in this patent, no detailed results have been reported on the grain size change.
Additionally, J. A. Christodoulides discloses a multi-layer thin film including FePt and carbon, and its structural and magnetic properties (J. A. Christodoulides, J. Appl. Phys. 87, 6938 (2000)). According to this document, the change of coercivity and fine structure of the multi-layer thin film is observed when a carbon content in the multi-layer thin film is varied. However, this technology is disadvantageous in that the multi-layer thin film is heat-treated at a relatively high temperature of 700° C. after a deposition process, and the high temperature causes various problems in a process of producing the multi-layer thin film. Another disadvantage is that a noise of a magnetic recording medium including the multi-layer thin film is increased because the multi-layer thin film has a nonuniform FePt grain size distribution. And also, the noise of the magnetic recording medium is increased because squareness ratio is decreased less than 1.